All Things Neutrinos

1. All Things Neutrinos H. Ray Los Alamos National Laboratory MiniBooNE

2. Outline • Neutrinos & The Standard Model of Physics • Oscillations • Sources of Neutrinos • Detecting Neutrinos • Interactions with matter • Detection techniques • Examples of detectors • Oscillation Results • Sampling of Neutrino Theories

3. Cool Neutrino Facts • Human body = 20 mg of Potassium 40. Humans emit 340 million neutrinos per day! • 100,000 billion pass through your body each second from the sun • Your body will stop ~1 neutrino which passes through it in a lifetime!

4. Why Neutrinos? • 2 body alpha decay, E of decay products always the same • 1913 - 1930 : beta decay = continuous spectrum of E • E not conserved? • P not conserved? • “I have done something very bad today by proposing a particle that cannot be detected; it is something no theorist should ever do.” (Pauli, 1930)

5. Two Body Decay Kinematics

6. Standard Model of Physics +2/3 -1/3

7. Standard Model of Physics 0 -1

8. Standard Model of Physics 0 1

9. Standard Model of Physics

10. Standard Model of Physics

11. Standard Model of Physics

12. Standard Model of Physics • Also have 12 anti-particles (same mass & lifetime, opposite charge) • Gauge particles mediate or transmit forces between particles • Forces that create particles also dictate which interactions particles can participate in • E-M : particles with electric charge • Quarks, leptons • Strong : binds quarks together • Quarks

13. Standard Model of Physics • Weak : force of transmutation! • changes flavor of quarks, leptons within a family • Only force that acts on neutrinos • Neutral current = no exchange of electric charge (Z) • Charged current = exchange electric charge (W+, W-)

14. Standard Model of Physics W+ W- W+ W-

15. Ex : Beta Decay duu = +2/3 n p dud = -1/3 W- W- = -1 e e- time

16. Neutrinos in the Standard Model • Neutrinos are massless • Neutrinos only interact via the Weak force • Neutrinos are left-handed • anti-neutrinos are right-handed • Neutrinos are electrically neutral • Neutrinos have three flavors • Electron, muon, tau

17. Oscillation Physics

18. Quark Mixing • Problem! If Weak force only acts inside of a family - how do you explain lambda decay? u u  d p d s u d W- - u

19. Quark Mixing • Solution : quark generations are rotated for the purposes of weak interactions • Instead of the Weak force coupling to • It couples to u u d d’

20. Quark Mixing • Where d’ is a linear combination of the d, s, b quarks • mixing that results from mis-alignment of weak and mass states is a natural outcome of the symmetry-breaking mechanism by which particles acquire mass Weak state Mass state d’ d Vus Vub Vud s’ = s Vcd b’ b Vtd

21. Quark Mixing • States which participate in Strong interactions are mass states • States which participate in Weak interactions are mixtures of mass states W+ W- ’ ’ ’

22. Lepton Mixing • Why doesn’t same thing happen to leptons? • SM = mass and weak states are identical because the neutrino has no mass! • If neutrinos are massive have analogous situation for neutrino-lepton pairs

23. Neutrino Oscillations Weak state Mass state cos  sin  e 1 =  cos  2 -sin 

24. Neutrino Oscillations Weak state Mass state cos  sin  e 1 =  cos  2 -sin  |(0)> = -sin  |1> + cos |2>

25. Neutrino Oscillations Weak state Mass state cos  sin  e 1 =  cos  2 -sin  |(t)> = -sin  |1> + cos |2> e-iE1t e-iE2t

26. Neutrino Oscillations Posc = |<e | (t)>|2 Posc =sin22 sin2 1.27 m2 L E

27. Neutrino Oscillations Distance from point of creation of neutrino beam to detection point m2 is the mass squared difference between the two neutrino states Posc =sin22 sin2 1.27 m2L E  Is the mixing angle E is the energy of the neutrino beam

28. Neutrino Oscillations sin22 Probability Distance from neutrino source (L)

29. Sources of Neutrinos

30. Neutrino Sources • Solar : ~ 0.1 - 15 MeV (106 eV) • from fusion inside of stars • 85% from p+p -> 2H + e+ + e • Man-Made : ~few MeV • Nuclear reactors - byproduct • Man-Made : ~ 0.5 MeV - 1 GeV (109 eV) • Accelerators - DAR, DIF • Atmospheric : ~1 - 10 GeV • cosmic rays = proton from outer space + atm = showers, creates atmospheric neutrinos

31. Solar Neutrinos ppI ppII ppIII Theoretical uncertainties

32. Nuclear Reactor Neutrinos Rb-92 e- • Reactors = only source of a pure anti-neutrino beam, pure electron-flavor beam! • Anti-neutrinos are emitted by the radioactive fissile products when they disintegrate via beta decay • ~few MeV Energy e

33. Accelerator-Based Neutrinos • Beam of protons + a target material = mesons (, K) • Mesons decay into the neutrino beam seen by a detector • K+ / + + +  • + e+ +  + e • K0L ++ - +  • Create neutrinos via meson Decay at Rest, Decay in Flight

34. Decay At Rest - absorbed by target E range up to 52.6 MeV Mono-Energetic! = 30 MeV +DAR Target Area Hg+ target, SNS (Spallation Neutron Source, Oak Ridge)

35. Decay At Rest • Advantage = Know timing of beam, lifetime of particles, use to greatly suppress cosmic ray background • Advantage = extremely well defined flux • Disadvantage = Low E limits choices of neutrino interaction signal • Disadvantage = Beam is isotropic - no directionality • Hard to make an intense isotropic beam

36. Decay In Flight • Advantage : more intense beam because mesons are focused (not isotropic) • Advantage : can select neutrino, anti-nu beam • Disadvantage : difficult to understand the flux (in content and in E)!

37. Atmospheric Neutrinos • High energy protons + nuclei collide in the upper atmosphere = high energy pions • Pions  muons + neutrinos • Muons  neutrinos • ( +): (e+e)= 2 : 1   e

38. Detecting Neutrinos Interactions with Matter

39. Detecting Neutrinos • Neutrinos interact with material in the detector. It’s the outcome of these interactions that we look for • Neutrinos can interact with : • Electron in the atomic orbit • The nucleus as a whole • Free proton or nucleon bound in nucleus • A quark

40. Neutrino Interactions • Elastic Scattering • Quasi-Elastic Scattering • Single Pion Production • Deep Inelastic Scattering MeV GeV

41. Elastic Scattering • Target left intact • Neutrinos can elastic scatter from any particle (electrons, protons) • Neutrino imparts recoil energy to target = how we observe these interactions e- e- Z e e

42. Quasi-elastic Scattering • Neutrino in, charged lepton out • Target changes type • Need to conserve electric charge at every vertex • Need minimum neutrino E • Need enough CM energy to make the two outgoing particles p n W+ e e-

43. Single Pion Production • Resonant • neutrino scattering from a nucleon • Nucleon resonance is excited, decays back into it’s ground state nucleon • Emits one or more mesons in the de-excitation process   Z0 N* N 0 N

44. Single Pion Production • Coherent • neutrino scatters from entire nucleus • nucleus does not break up / no recoil nucleon • Requires low momentum transfer (to keep nucleus intact) • No transfer of charge, quantum numbers   Z0 0 A A

45. Deep Inelastic Scattering Hadron shower • Scattering with very large momentum transfers • Incoming neutrino produces a W boson, turns into partner lepton • W interacts with quark in nucleon and blows it to bits (ie inelastic) • Quarks shower into a variety of hadrons, dissipating the E carried by the W boson (ie deep) n W+ e e-

46. How often do these interactions occur?

47. Cross Sections • Cross section = probability that an interaction will take place Volume of detector = V (m3) Density of nucleons = n (1/m3) Neutrino flux =  (1/m2s)      Cross Section  (m2) = # neutrino interactions per second Flux * Density * Volume # of targets

48. Neutrino Cross Sections

49. Detecting Neutrinos Detection Techniques

50. Observing Neutrino Interactions • Very small cross sections for interactions! • Need large-scale detectors • Radiochemical reactions • e + 37Cl = 37Ar + e- • Measure neutrino flux by counting number of produced Ar atoms • No time, direction information • Passage of charged particles through matter leaves a distinct mark • Cerenkov effect / light • Scintillation light • Provides time, direction information Find s Find products of  ints